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How to see Comet PanSTARRS (C/2011 L4) in March 2013

After much build up and anticipation Comet PanSTARRS (C/2011 L4) will finally arrive and light up the early evening skies during March. Early predictions forecasted a spectacular display, a dazzling naked-eye comet, rivaling in brilliance the night sky's brightest stars and blazing an unforgettable trail above the western horizon just after sunset for a few days in March.

Sadly, recent observations suggest than PanSTARRS will be much dimmer than originally estimated. Even so, it should still reach naked-eye visibility and it certainly would be bad luck if we were denied a good view of this icy-rock, at least with a pair of binoculars or a telescope.

Recent observations

So far this year PanSTARRS has been a southern hemisphere comet. To a lesser extent it was also visible from the tropics but not from northern temperate latitudes. For the first 6 weeks of 2013, the comet brightened only modestly but just when it seemed we might have a celestial flop on our hands, it suddenly produced a small but noticeable increase in brightness. This small burst of activity coincided with the first batch of naked eye sightings as PanSTARRS hit magnitude 5.4 (February 15th). Only four days later, the comet was now a nice early morning object for southern hemisphere observers. Despite been only a few degrees above the horizon it was visible with the naked eye, even against the bright twilight background. The coma of the comet was concentrated with a short broad tail of at least 30 arc minutes in length. Estimates at this stage put the magnitude at 4.5. The comet then continued to brighten as it switched from the morning to the evening sky. On February 27th, PanSTARRS was now magnitude 3.4 with the coma and tail clearly visible to the naked eye. When viewed through 10x50 binoculars the tail measured more than 1 degree in length and of course extended much further when imaged or photographed.

Location, magnitude and star chart

As PanSTARRS heads northwards against the background stars, visibility switches from observers located in the southern hemisphere to those in the north. The comet on February 27th was located in Sculptor at a declination of 30S and visible as an evening twilight object for southern hemisphere observers, although very low down. For those in the northern hemisphere it was not visible but their waiting time is now almost over.

PanSTARRS continues on an essentially northeastern path. From Sculptor, it then cuts through a corner of Aquarius before heading into Cetus on March 5th. It then makes a short diversion into Pisces (March 9th to March 11th), then back into Cetus for two further days before returning to Pisces on March 13th. This is the period of peak brightness when PanSTARRS reaches perihelion or closest approach to the Sun (March 10th). On this date we estimate a magnitude of 1.6, although given the unpredictability of comets, it could easily be brighter or dimmer than that. What is certain, the comet will be positioned extremely close to the Sun in the sky and as always extreme care must be made when observing in such cases. Never casually sweep for the comet with binoculars or a telescope if the Sun is above the horizon. Make sure that the Sun is below the horizon. Even the shortest glimpse of the unfiltered Sun with binoculars or telescopes can cause permanent eye damage. It's just not worth the risk.

The comet then heads due north for a while, crossing into Andromeda on March 22nd and into Cassiopeia on April 9th before arriving in Cepheus at the end of the month. By now PanSTARRS will be circumpolar for most observers located in the northern hemisphere.

For southern hemisphere observers PanSTARRS is visible very low down in the western sky during evening twilight until about the second week of March when it is lost to the Sun. Observers based in the northern hemisphere have it much better. They can expect to follow PanSTARRS as a naked-eye object from about March 12th until April 1st. The comet is best seen in the evening sky during this time although from about the third week of March it may also been seen in the morning skies, before becoming circumpolar from most northern locations in early April. Its magnitude will decrease from 1.7 on March 12th to 3.7 on March 22nd and down to 5.5 by April 1st. With a bit of luck, it should display a nice long tail. On March 12th, PanSTARRS is joined by the extremely thin crescent two-day old Moon.

The diagram below shows PanSTARRS as seen from temperate northern latitudes.

For example from New York, USA (40N) the comet is about 10 degrees above the west-northwest horizon from March 15th to April 1st, 45 minutes after sunset. This covers the period of naked-eye visibility. After that the comet will be higher in the sky but now beyond naked eye visibility and requiring at least binoculars to be seen. By April 13th it will located a declination of 50N and therefore circumpolar from anywhere north of 40 degrees latitude; hence visible all night, but down to 7th magnitude in brightness.